1. Field of the Invention
In a warehousing situation there is an on-going task of transferring pallets of merchandise between the inside of a trailer parked at a loading dock and various locations at various levels in rows of multi-tiered storage racks. Whether loading trailers or unloading trailers, the endpoints of the process remain the same: trailers on one end and multilevel storage rack locations on the other end. The forklift spends a significant percentage of its operating time traveling between these two areas, carrying one pallet at a time as it does so. This is especially so in very large warehouses.
If a way could be found to inexpensively and quickly and easily enable the forklift to transport two pallets at a time instead of one there would be a significant increase in the forklift's efficiency, which is what this invention accomplishes.
There are immediate benefits because handling time is reduced on a trailer-by-trailer basis, and there are longer term benefits due from the cumulative reduction of labor costs and usage time and mileage accrued on the forklift. Other advantages include statistical reduction in collision type accidents because the number of back and forth trips is reduced for an equivalent number of pallets, and there is a reduction in fuel use and/or battery use.
The novelty of this invention is that it introduces into a warehouse environment a comparatively inexpensive and simple way to improve the horizontal transport efficiency of a forklift in an environment where previously the forklift has been provided with multiple pallet transport capacity by installing expensive attachment equipment which typically requires purchasing a bigger, more expensive forklift to handle the additional pallet weight provided for by the attachment device.
2. Description of Related Art
The concept of transporting more than one pallet at a time by a forklift per-se does exist to a limited extent. The mast of a forklift is equipped with a support frame that is wide enough to hold two sets of forks. The pairs of forks are positioned symmetrically to the left and to the right of the mast. The operator can insert the two sets of forks simultaneously into two pallets side by side, lift them, transport them to a desired location, and place them simultaneously at their new location. However; there are significant limitations. First of all, the pallets of merchandise must be of the same weight otherwise there would be a left/right balance issue. Secondly the combined weight of the pallets must be less than the lifting/tipping capacity of the forklift. Because of these limitations the application of this type of device is restricted to situations where the pallet loads are homogenous and very light unless a forklift with greater lifting capacity is used. A typical example is a warehouse which stores pallets of unfilled soda cans before they are shipped to the bottling plant. Note that this device MUST lift two pallets at a time if they are side by side. It can't select a single pallet from a fully loaded rack. It has to select two pallets because the twin fork assembly is fixed. Both sets of forks are raised and lowered at the same time.
There is a second type of device which is similar to the first device but has somewhat more versatility. Imagine a typical set of forklift blades (two blades). Then imagine slicing each of the forklift blades along its length. Set up linkage and hydraulics that joins the left hand slices of each blade together, and linkage that does the same for the right hand slices. Then provide hydraulics and control devices that move each pair of linked slices independently. Using the controls the operator can move each pair of half wide blades to set up a twin set of fork blades and consequently be able to lift two pallets at a time as with the first device. However this device has more handling versatility because the operator can move the sets of half blades together to form a single set of blades, extract a single pallet from the storage racks, transport it to another rack location and place it on the floor. A second pallet can be extracted from the racks and placed on the floor beside the first pallet. The operator can than re-position the sets of half fork blades to form two sets of blades and then use them to pick up both pallets simultaneously. If the operator starts with two pallets and wants to place them in different locations he simply re-configures the forks in the appropriate manner and proceeds. Again all of the weight and balance restrictions of the first type of device still apply. These devices are generically termed double pallet handlers or multiple pallet handlers.
Although not a forklift per-se, there is another example of a piece of material handling equipment transporting two pallets at a time. This piece of equipment is a pallet jack which has forks that are twice as long as those of a standard pallet jack. Two pallets are positioned one behind the other. The pallet jack with the extra long forks is inserted into the first pallet. As the jack is pushed forward the forks go into the second pallet as well. When the operator raises the jack both pallets are lifted, and can be transported as the operator then moves the jack.
Another area where prior art exists is the device which is used to couple/interface the forklift to the cart. U.S. Pat. No. 4,884,936, issued Dec. 5, 1989 to Kawada, shows a pallet jack of reduced dimensions with respect to a standard pallet jack that has been equipped with a flange on the vertical part of the body of the jack. The pallet jack, in its lowered condition, is driven underneath the cart with the vertical part of the jack body against the bottom edge of the cart the edge of which has also been equipped with a flange. The jack is then raised and the flange on the bottom edge of the cart is secured between the flange on the pallet jack and the vertical part of the body of the jack. This method of engagement is nearly identical to the method that will be described later where the horizontal blades of a forklift are equipped with vertical projections and the fork blades are driven under a cart and the blades are the raised thereby engaging with a plate beneath the edge of the cart. The physical device in the Kawada patent is basically a customized pallet jack. It is used to interface with a 4-wheel cart (all castors) that has a frame structure above it for holding boxes of merchandise. Note that in the Kawada invention the entire customized pallet jack is considered to be the invention.
Another example in which a pallet jack is equipped to interface with a cart is shown in a U.S. Patent Application Publication No. 2008/0181760 by Frahm et al. In this invention a device is mounted between the straddle forks of the pallet jack right at the front tips of the forks. Its method of engaging with a cart Is similar to that used by Kawada with two major differences. In the Kawada application the dimensions of the Kawada device are made narrow enough to allow the outside edge of the forks to go between the wheels on the end of the cart and consequently go under the cart. In Frahm/Mehle a pallet jack of standard width is used and the forks cannot go underneath the cart from the end. The second factor is that the Frahm/Mehle device is equipped with swivels and slide adjustments so that it can interface with the cart even on an uneven surface. The Kawada device has no such feature. The invention of Frahm/Mehle is considered to be an attachment only, not an entire custom powered pallet jack as in Kawada.
Both the Kawada device and the Frahm/Mehle device involve pallet jacks only. A pallet jack can only lift a load several inches from the floor surface and must deposit that load back on the floor surface. A forklift has extended vertical lift ability and can place a load or retrieve a load from a level well above the floor level upon which it rests. U.S. Pat. No. 5,236,299 by Oskam describes a device to be connected to a trailer (a cart with wheels on one end and a support stand on the other end) where the device has two offset parallel metal bars. The fork blades of a forklift are inserted in between the bars which are at the support stand end of the trailer and then the forks are raised slightly thereby lifting the support stand off the ground. The offset parallel bars trap the fork blades and the binding friction between the bars and the fork blades allows the forklift to move and turn with the trailer.
It is noted that the specific means to connect the cart to the forklift is not an essential aspect of the invention. The fact that a means of some kind be used is necessary but the specific way is optional.
In the context of prior art, if it was desired to provide a forklift with the ability to transport multiple pallets at a time, the forklift had to be fitted with an expensive hydraulic/mechanical device. There was the high cost of the device itself. Then there was the cost of installing the device on the forklift. Then depending on the size of the forklift already in use there was the cost of upgrading to a heavier/stronger forklift to handle the added lifting capacity that the multiple pallet device provided. The present invention enables a forklift to transport two pallets at a time with minimum or no modifications to the forklift and a much less expensive cart.